Coal fired furnace



Aug. 2, 1966 w. w. RorasoN, .JR 3,263,655

COAL FIRED FURNACE Filed Oct. 25, 1963 2 Sheetfs-Sheet 1 FIG. l

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INVENTOR FIG. 5 //Y//m W Pabso/zL//r Aug 2, 1966 w. w. RoBsoN, JR 3,263,655

COAL FIRED FURNACE Filed Oct. 23, 1963 2 Sheets-Sheet B N VENTOR.

Mmm W www AT T'Y.

United States Patent O 3,263,655 CGAL FIRED FURNACE William W. Robson, Jr., 1621 Highland, Wilmette, Ill. Filed Oct. 23, 1963, Ser. No. 318,362 5 Claims. (Cl. 122-376) This invention relates generally `to furnaces burning hard 'fuels -sudh as coal `to heat Water and particularly to -improvements in water-cooled station-ary grates and furnace walls.

`Most coal-fired boiler furnaces have water-cooled walls around the combustion chamber lfor heat conservation, eificiency, and wall life. Also water-cooled rgrates have been employed as integrally supported on rWater jackets set in ythe combustion chamber and connected by pipes to the boiler. The coal is supported on the -grates and supplied with air for burning. Grates employed have taken various forms, many of them traveling or reciprocating to handle the coal, advance the fuel bed and discharge the ash automatically while permitting primary air and secondary ,air -to be supplied thereto, Ifor combustion purposes, preferably under forced draft. However, most of `the grates are stationary and are either of a shaker type if the 'furnace is lfed by hand or by a spreader, or are of lan inclined bar type down Wh-ich the coal 4is 'advanced by reciprocating pusher blocks.

The grates are `generally made of comparatively inexpensive alloyed cast iron and in order to prevent their rapid deterioration, it is highly desirable to cool the grate elements that -are in direct contact with the hot coals. Cooling can be acomplished in several Ways, and although some cooling is `accomplished with the flow of primary lair through the grates, this is minor and actualily results in Agreater heat inducement in the coals contacting the grate. However, main cooling can be accomplished either by air with special grates for great fuel economy as described .in my co-pending application Serial No. 130,858, or, by water. Preferably the water is circulated from tlhe boiler so that .the thermal units of combustion rejected through the grates to the cooling Water are conserved for boiler heating.

Water-cooled grates are of particular interes-t in the present invention and preferably contemplate ladder-like cooling units in which a series of parallel stationary water pipes is inclined lengthwise ydownwardly from the coal door or feeder to the ash pit. Although one cooling unit generally suffices, two or more can be used arranged in successive steps or stages. -Each cooling unit includes vheader tubes cross `connecting the ends of the parallel water pipes as 'a mani-fold and supporting them free of any intermediate weight bearing elements that might contact lthe cooling unit.

Heretofore, the header tubes have in turn been integrated -at opposite ends With flat elongated Water tanks or jackets sometimes referred to -as water Walls along with supporting legs and bracers. Tuyeres are then fastened in place and the integrated assembly is then shipped and when received it is slid into the combustion chamber, shored up and connected by pipes to the boiler. Combustion chambers or furnace compartments involve a wide range of shapes and sizes and without any standardizations being established, each integrated assembly has to be made up special for each furnace either as original .or replacement equipment 'and are quite expensive. Replacement orders require months to lill and involve irritating and costly delays.

Although much of this special treatment and handling is excused on the grounds of attaining the greatest efiiciency in the space available for economically operating the furnace, such still is not -attained to the fullest possible extent. The -available furnace space for maxi- ICC mum grate air is materially reduced and either the furnace is designed to be oversized because of this or the on cycle becomes lengthened to make up for it for a same furnace rating.

Also installing such a bulky unitized article with adequate clearances in the fui-ance space contributes many diicultes, particularly in close quarters. Moreover, since assembly, shipping, yand installation strains `accompanying the installation and replacement of a bulky unitized article might cause damage to the assembly and also ydiscrepancies in special dimensions might require some springing of the elements to get them to makeup, all of Iwhich is generally experienced 'with special orders, the `assembly is beefed up with extra stock and l Vsize a great deal more than otherwise required. This is a further burden -on the price, the cost of shipping and of labor in handling.

Furthermore, lvery often the water cooling elements themselves do not require replacement but only tuyeres carried by the pipes and tubes. The tuyeres directly contact the bed of hot coals and conduct primary air to the bed and may deteriorate more in one spot than another. Also, they are clamped -in intimate heat exchange contact 1with the pipes and tubes and any overclamping may `damage the pipes while underclamping endangers rapid deterioration of tuyeres for lack of proper cooling.

Accordingly, one of the objects of the present invent-ion is to provide a Water-cooled grate unit as an inventoried stock item for rwide ranges of furnace sizes, irrespective of shapes, which is simple in construction, which can be cut to a slight oversize on the joh and installed with minimum time and expense lwith conventional tools used by furnace men.

Another object is .to provide an improved assembly arrangement for tuyeres which can be properly installed after the cooling unit portion of the grate has been installed, or 'which can be assembled with tlhe cooling unit on the `spot to provide a unitized grate as original or replacement equipment.

A further `object of the invention is to provide a clamping device which automatically provides the proper clamping tightness for tuyeres With the use of standard hand wrenches Without any protruding elements remaining to be engaged and eroded by the hot coals, yet can be easily removed for replacement of one or more tuyeres at any time.

The invention is characterized by an improved mounting of a Water-cooled grate which makes available the entire furnace space as the combustion space. The grate is readily installed Iwith minimum time and expense in fused or Iwelided relationship `directly to the water cooling walls of the boiler itself for better 'wa-ter circulation yet can be cut Ifree quickly land easily, removed and replaced 'W-ithout damage to the boiler or any coal handling mechanisms therein.

A further object off the invention is to provide standard lengths of water-cooled 'grates which can be cut and fitted .on the job to any width for installation in any furnace 'with or 'Without utilization of any special equipment that might be present including extra wvater Walls, coal pushers and Wind -boxes or plenums.

A further object of the invention resides in a multistep grate arrangement with the primary air plenum sealed in an improved Way against movement of air except through the tuyeres.

A further object of the invention is to provide an improved water-cooled grate construction which is inexpensive to make, use and service, easily handled as a standard item for different installations and which is economical of materials and readily handled or assembled with standard tools.

'Ihese being among the objects of the inventionxother and further objects will be noted from the description to follow taken in conjunction with the accompanying drawings in which:

' I FIG. 1 is a side elevation of a heating plant partly in ysection longitudinally through the furnace portion showing the grate and associated devices.

FIG. 2 is a plan view of the pipe and tube assembly portion furnished as a stock item.

FIG. 3 is a vertical cross-sectional view through the furnace at a header tube of the grate with a portion taken a short distance therefrom.

FIG. 4 is a section taken on line 4-4 of FIG. 3.

FIG. 5 is a perspective view o'f a tuyere assembly prior to their clamped securement.

FIG. 6 is a side elevation of a preferred form of securement means for the tuyeres.

Referring now to FIG. 1, a heating plant comprising a boiler 10 having end walls 12 and side walls 14 defining a furnace space 16 is shown with two partially overlapping water cooled grates 18 embodying the invention. The grates are inclined downwardly and rearwardly towards the ash pit 20. The upper front grate 18]c has its upper end in close proximity to the bottom of the coal hopper 22 from which it is fed fresh coal by a spreader device or a pusher block 24 that is made of a U-beam section and reciprocated conventionally in controlled relationship with a leg and a part of the web of the beam section closing the coal opening 25 in its resting position between pushes.

The lower rear end 26 of the front grate 18jc is spaced above and overlaps the front end of the rear grate l8r. Hot coals moving from off the 'lower end of the front grate drop upon the front end of the rear grate. A second pusher block 28 coordinated with the first and reciprocating in the space between the overlapping ends keeps the coals moving across the face of the rear grate. The resting position of the second pusher block is in retracted position. The resting positions of the pushers between pushes are implemented for the full use and supply of primary air upwardly through the grates to the coals on top thereof without any loss thereof through the pusher openings.

The construction of thecooling units of the grates is shown in FIG. 2 in which water pipe tubes forming cross headers 30 serve as manifolds for a ladder of longitudinally extending water pipes 32 that are preferably spaced from one another a distance approximately equal to their outside diameter. Although the spacing can be graduated from their median outwardly, it has been found that with the headers connected directly to the sides of the water wall of the boiler to embody the invention, equal spacing of the pipes 32 for manufacturing convenience is adequate even for a continuously heavily fired boiler.

A characteristic of the invention is that the headers 30 can be supplied in several predetermined lengths and the length differential therewith involved with many `different widths of individual furnace spaces are corrected by cutting down the length of longer header to the length desired. In conjunction therewith the water walls are apertured with vertically spaced openings 34 for grate incline, at distances equal to the spacing 'of the headers 30. The headers 30 are then cut to a desired |length few inches greater than the width between the walls. Thereupon the headers are inserted at one of their ends into the openings 34 on one of the water walls whereupon the other ends of the headers are lifted and the cooling unit slid reversely into the openings on the other water wall until equal lengths of the headers extend into the water wallsabove the mud ring. Thereafter, the joints around the headers at the openings are seam welded at 36. The boiler is then pressure tested against leaks.

By way of assisting this installation, collars 38 can be welded in the openings as located by a sheet metal grid template (not shown) and stops 39 placed on sald other end of the headers to locate the headers ends at equal depths in the respective openings. Collars need not be used where the tuyeres are to extend to the boilers water jacket wall. The seam weld can be directly between wall and tube. Thereby an uninterrupted at wall surface is provided against which the tuyeres can be fitted throughout their length.

Where collars are employed the headers can be brazed in place to the collars (lower melting point) and then when the grates are replaced the headers can be flame or saw cut adjacent thereto. The cooling unit would then be dropped and removed and the stubs unbrazed for removal without any need to rework the water walls of the boiler. However, it has been found that a direct weld of the headers to the water walls seldom if ever is `disturbed because of the increased longevity of the grates embodying the invention.

It should be noted that wear and corrosion on the tuyeres may require their renewal or servicing, in whole or part, several times during the life of the cooling unit. For this purpose, the preferred construction of a tuyere 46 is shown in FIGS. 3 through 5 as having a crosssectionally T-shaped member whose head delines arms 50 resting on the pipes and terminating halfway over adjacent pipes 32. A central leg portion 52 extends downwardly between the pipes a little distance short of the bottom extremity of the pipes. The underside of the arms 50 and the top edges of the leg closelylfollow the contour of the pipes 32. Bolt holes 54 are cast in the leg portionsV and are recessed at the top at 56 to receive a rounded head 58 of the bolt 60. Cross tie bars 62 engage bottoms of the tuyere legs 52. The bolt ends extend through the tie bars to receive nuts 64 thereon.

The bolts 60 are of a novel construction, to be described, to clamp the tuyeres 46 snugly in place with a high heat conductive aluminum plastic bonding material 69 squeezed between the tuyeres and pipes and between the tuyeres themselves at their sides and ends for transmission of heat between them at a high rate.

Also, vertically through the legs 52 one or more rows of air holes are cast or drilled for the movement of the primary air from the plenum 31 to the coal on the tuyeres for a clean burn out.

Referring now to the construction of the bolts 60, these bolts constitute bolt portions 58 having circular head portions 68 received snugly in circular recesses 56 Hush with the top of the tuyeres and also embedded in high heat conductive aluminum plastic. As an auxiliary element threaded into or made integrally with the head 58, a wrenching head portion 70 is provided that is undercut as at 72 to provide a weakened section which will 'break away when a predetermined tightening torque force is exerted thereon. The break-away head 70 may have an externally hexagonal contour, as shown, or an internal Allen wrench socket. Either way they are designed to receive standard wrenches. Thus, the bolts 58 can be tightened manually or with power wrenches with any exertion of torque forces desired, but when the proper tightness is reached, the^wrenching element 70 will break olf leaving an upper face end flush with the upper tuyere surface with adequate clamping elfort and without damage to the pipes 32.

The lower end of the bolt can be threaded into the tie bars 62 themselves directly, or, preferably as shown, into nuts 64 so that later onwhen it becomes desirable to remove one or more tuyeres the appropriate nuts v64 can be loosened with the hardened aluminum plastic around the heads 68 holding them against turning for the ready release of the bolts 58 and removal of the tuyere.

The tie bar 74 along the lower rear end of the front grate 18]c is constructed to provide a running air seal fit with the front end of the rear grate 18r and preferably this is accomplished with the tie bars 74 being cast in sections with a downwardly opening groove 76 spaced from the rear edge of the front grate 18]".

An air sealing element 78 is gravity mounted in the groove 76 as supported by pins 80 press fitting or threaded into place in the tie bar 74 with the ends intersecting the groove 76 and being received in vertically elongated slots 82 in the sealing element. In this connection it is to be noted that the front upper corner of the push block 28 is beveled at 83 so that the block can be removed rearwardlyfrom under the forward grate 18f when desired Iand returned without blocking interference therewith. The bevel 83 cams the sealing element upwardly without otherwise disturbing the assembly upon such occasions.

The sealing element 78 is laminated with a bronze rear layer 84 and an iron front layer 86. As initially provided the bronze layer extends slightly below the iron layer on the bottom edge. This permits the bronze under the weight of the sealing member to wear rather rapidly into a contour matching the surface irregularities of the pusher block and when the iron, preferably an alloy metal, begins to make contact with the pusher block, it carries the weight and further wear is inhibited on the bronze leaving a close working seal of excellent longevity between the two elements .and thereby preventing loss of pressure from the plenum. It should be noted that the air pressure is effective against the front of the sealing element and the bronze layer is on the back side in conta/ct with the back wall of the groove. The organization is thereby favorable to the seal maintained even with extra loose manufacturing tolerances that assist assembly and fitting of cooperating members. Thereby they generally can be made of sand castings with very little machine finishing being required for excellent operation.

By way of further understanding of the invention the furnace is provided with the opening 25 (FIG. 1) across the bottom front end and if an ignition arch is not already provided such is installed by drilling holes through the front end wall 12.1c :as at 11 and into the rear end wall 12r as at 13 whereupon the ignition arch tubes 15 are slipped through the front wall 12]c and welded into place to receive fire brick 17 thereon. The external entry openings are then plugged as at 19.

The side walls 14 are drilled out and the headers 30 of the cooling units cut to length and installed as already described. The tuyeres 46 are fastened in place with any gaps between the grate tuyeres and the side walls sealed with furnace cement 21 (FIG. 3) whereupon a compact operating unit which includes the main Iblower 87, the push Iblock activating mechanism 89 are fitted at the center front of the opening 25 with the push blocks 24 and 28 cut to proper lengths, installed and hooked up to actuating push rods 91. The control equipment is then hooked up and the electrical power connected ready for operation. It should be noted at this time that the relative elevation of the components is to locate the lowest header of the grates just above the mud line of the furnace and the ignition arch between 18 and 22 inches above and parallel with the grates.

Ignition is established in the usual way with a bed of coal advanced on the front grate and thereafter the main blower 87 provides primary air for peak firing as controlled by adjustable damper 93. Primary air to the rear grate is supplied through aperture 95 as controlled by damper 97.

Whereas the grates dis-closed in said application Serial No. 130,858 maintain combustion temperatures in the .coals thereon when air pressure is shut down on the olf cycle, the cooling eiciency of the present invention for the longevity of inexpensive tuyeres is such that the coals can be chilled below their ignition temperature.

While it is possible to turn on and off the main blower approximately every minutes during off-peak firing periods for a minute or two to maintain ignition, it is preferred to provide the small, economical auxiliary blower 86 of low capacity for continuous service during off-peak firing periods to fan the coals and maintain ignition. Although iiue conditions might maintain such ignition in some installations, it is preferred that such be assured by the small blower. Accordingly, a miniature auxiliary blower having a conduit size of approximately 'l to 2 inches in diameter runs on the off cycle to fan the coals with enough air to sustain combustion temperatures between on cycles.

Having thus explained and described this invention, the functions and preferred constructions of the elements, it will be understood by those skilled in the art how the objects are attained and how other and further changes can be made in the preferred embodiments shown without departing from the spirit of the invention, the scope of which is commensurate with the appended claims.

What is claimed is: t

1. In combination with a boiler having a coal feed opening and a fuel combustion space therebeyond defined laterally by vertical water walls defining la water space on one side, a grate comprising two horizontally spaced header tubes in said combustion space interconnecting and extending at their opposite ends through said water walls in sealed relationship therewith and in open com- -munication with said water space therein, the header tube adjacent to the feed opening being disposed below the level of the feed opening and the header tube remote from the feed opening being disposed below the level of the first mentioned header tube, a plurality of coplanar water pipes interconnecting said header tubes spaced from each other in a direction lengthwise of said headers and at their ends in open communication therewith, plural rows of end abutting tuyeres having legs disposed between each pair of asid pipes land abutting the edges of adjacent rows of tuyeres above the center of said pipes, said legs terminating downwardly at a planar level above the plane of the lowest sides of said pipes, transverse tie bars engaging the lowest sides of said pipes, metal clamping means flush with the top of the tuyeres extending through said legs Iand tie bars for clamping said tuyeres against said pipes, high heat conductive means intimately intercon- `necting theinterfaces of said tuyeres and pipes and said tuyeres and clamping means.

2. In combination with a boiler having a coal feed opening and a fuel combustion space therebeyond defined laterally by vertical water walls defining a water space on one side, a first grate comprising two horizontally spaced header tubes in said combustion space interconnecting and extending at their opposite 'ends through said water walls in sealed relationship therewith and in open communication with said Water space, the header tube adjacent to the feed, a plurality of coplanar water pipes interconnecting said header tubes in open communication therewith, plural rows of end abutting tuyeres having legs disposed between each pair of said pipes and abutting the edges of adjacent rows above the center of said pipes, means for clamping the tuyeres on said. pipes including a rear element engaging in part a header tube and having a downwardly opening groove therein, a4 second grate below the first, a coal push block reciprocably received between the grates where they overlap, and air sealing means slidable in said groove and resting on said push block in sealed relationship.

3. In combination with a boiler having a coal feed opening and a fuel combustion space therebeyond defined laterally by vertical water walls defining a water space on one sid'e, a iirst grate comprising two horizontally spaced header tubes in said combustion space interconnecting and extending at their opposite ends through said water walls in sealed relationship therewith and in open communication with said water space, the header tube adjacent to the feed, a plurality of coplanar water pipes interconnecting said h'eader tubes in open communication therewith, plural rows of end abutting tuyeres having Ilegs disposed between each pair of said pipes and abutting the edges of adjacent rows above the center of said pipes, means for clamping the tuyeres on said pipes including a rear element engaging in part a header tube and having a downwardly opening groove therein, a second grate below the first, a coal push block reciprocably received between the grates where they overlap, air sealing means slidable in said groove and resting on said push block in sealed relationship, an air plenum below said first grate, means for intermittently' supplying primary air to said plenum during on-peak burning cycles, and means for supplying a low volume of air to said plenum alternately for fanning the coals to maintain ignition during olf-peak burning cycles.

4. In combination with a boiler having a coal feed opening and a fuel combustion space therebeyonddefined laterally by vertical water walls defining a water space on the sides, a iirst grate comprising two horizontally spaced header tubes in said combustion space interconnecting and extending at their opposite ends direct-ly through said water walls, means for securing the ends of the header tubes in sealed relationship with the water walls and in open communication with said water space, the header tube adjacent to the feed opening being disposed below the level of the feed opening and the header tube remote from the feed opening being disposed below the level of the first mentioned header, a plurality of coplanar water pipes interconnecting said header tubes spaced from each other in a direction lengthwise of said headers and at their ends in open communication therewith, plural rows of end abutting tuyeres having legs disposed between each pair of said pipes and abutting the edges of adjacent rows above the center of said pipes, said rows of tuyeres extending to a point below said opening, means for feeding coal through said opening onto the top of said tuyeres, said legs terminating downwardly at a planar level above the plane of the lowest sides of said pipes, transverse tie bars engaging the lowest sides of said pipes, the tie bar along the rear end of said grate having a groove therein opening downwardly, metal clamping means liush with the top of the tuyeres extending through said legs and tie bars for clamping said tuyeres against said tubes and pipes, high h'eat conductive means intimately interconnecting the interfaces of said tuyeres and pipes and said tuyeres and clamping means,

a second grate below the rst grate at said groove, pusher means siding on said second grate below said groove, air sealing means slidable vertically in said groove and engaging said pusher means in air sealed relationship, and air plenum means below said first grate.

5. In lcombination with a boiler having a coal feed opening and a fuel `combustion space therebeyond delined laterally by vertical water falls defining water spaces on opposite sides of said combustion space, two inclined vertically spaced grates in marginal overlapping relationship, each grate comprising two horizontally spaced header tubes in said combustion space interconnecting and extending at their opposite ends through said water Walls in sealed relationship therewith and in open communication with said water spa-ces, a plurality of coplanar water pipes interconnecting said header tubes spaced from each other in a direction lengthwise of said headers and at their ends in open communication therewith, plural rows of end abutting tuyeres having legs disposed between each pair of said pipes and abutting the edges of adjacent rows above the center of said pipes, said legs terminating downwardly at a planar level above the plane of the lowest sides of said pipes, the upper header tube of the front grate adjacent to the feed opening being disposed below the level of the feed opening and the header tube remote from the feed opening being disposed below the level of the first mentioned header, the upper header tube of the grate remote from the feed opening being disposed below the level of said remote header tube of the front grate and the lower header tube of said remote grate being above the mud ring of the boiler; push block means reciprocating between said grates at said overlap, air seal means between said front grate and said pusher block means, and primary air plenum means below said front grate.

References Cited by the Examiner UNITED STATES PATENTS 1,795,127 3/1931 Hobbs 122-373 2,057,450 10/ 1936 Schrenk 122-2 2,099,827 11/ 1937 Schrenk 122-2 3,005,446 10/1961 Kock 122-376 3,027,881 4/1962 Sams 122-373 3,081,747 3/ 1963 Guillou-Keredam 122-376 X KENNETH W. SPRAGUE, Primary Examiner. 

1. IN COMBINATION WITH A BOILER HAVING A COAL FEED OPENING AND A FUEL COMBUSTION SPACE THEREBEYOND DEFINED LATERALLY BY VERTICAL WATER WALLS DEFINING A WATER SPACE ON ONE SIDE, A GRATE COMPRISING TWO HORIZONTALLY SPACED HEADER TUBES IN SAID COMBUSTION SPACE INTERCONNECTING AND EXTENDING AT THEIR OPPOSITE ENDS THROUGH SAID WATER WALLS IN SEALED RELATIONSHIP THEREWITH AND IN OPEN COMMUNICATION WITH SAID WATER SPACE THEREIN, THE HEADER TUBE ADJACENT TO THE FEED OPENING BEING DISPOSED BELOW THE LEVEL OF THE FEED OPENING AND THE HEADER TUBE REMOTE FROM THE FEED OPENING BEING DISPOSED BELOW THE LEVEL OF THE FIRST MENTIONED HEADER TUBE, A PLURALITY OF COPLANAR WATER PIPES INTERCONNECTING SAID HEADER TUBES SPACED FROM EACH OTHER IN A DIRECTION LENGTHWISE OF SAID HEADERS AND AT THEIR ENDS IN OPEN COMMUNICATION THEREWITH, PLURAL ROWS OF END ABUTTING TUYERES HAVING LEGS DISPOSED BETWEEN EACH PAIR OF SAID PIPES AND ABUTTING THE EDGES OF ADJACENT ROWS OF TUYERES ABOVE THE CENTER OF SAID PIPES, SAID LEGS TERMINATING DOWNWARDLY AT A PLANAR LEVEL ABOVE THE PLANE OF THE LOWEST SIDES OF SAID PIPES, TRANSVERSE TIE BARS ENGAGING THE LOWEST SIDES OF SAID PIPES, METAL CLAMPING MEANS FLUSH WITH THE TOP OF THE TUYERES EXTENDING THROUGH SAID LEGS AND TIE BARS FOR CLAMPING SAID TUYERES AGAINST SAID PIPES, HIGH HEAT CONDUCTIVE MEANS INTIMATELY INTERCONNECTING THE INTERFACES OF SAID TUYERES AND PIPES AND SAID TUYERES AND CLAMPING MEANS. 